So when at the signing, I asked Brandon just how many secret societies were on Roshar.
The answer: THERE ARE NINE CURRENTLY WORKING.
So far, I've worked out about six. Again: Slight Spoilers!
1: The 17th Shard (Brandon Confirmed)
2: Ghostbloods
3: Mr. T and the followers of the Diagram
4: Sons of Honor
5: Skybreakers
6: Envisagers? (Teft's family)
7: ?
8: ?
9: ?
Did anyone catch any I missed?

I would think that tin wouldn't help much with seeing spren unless it helps the user see into the cognitive realm.
The mist, so far as I know, exists in the physical realm. So there's no precedent for tin helping see anything cognitive, even if "tuning in" works on Roshar as well as it does on Scadrial.

Luck I'd bet! Storing luck with Feruchemy can make you less likely to be involved in important events, the reverse is true when you draw on it. Also:rolling dice or spinning weapons ala Matt (Towers of Midnight) to decide where to go sounds like a very Hoidish thing to do.Edit: actually, that would be an Atium piercing wouldn't it? Oh well, for all we know, he might have one of those too.

Mine is simple, Brandon knew my uncle from college and based captain Goradel on him. My username here was Goradel's nephew until I'd showed up to enough signings that Brandon dubbed me Aaradel. This is the only place I use it as my forum name though. I use different usernames all over the place.

Kirk, you're forgetting spanreeds. If stormlight infused gems and spren can sync to each other across vast distances, there may be a functional equivilant for Scadrial. Especially considering the "Magic Technology" Brandon has said exsists there.
It might work, but I'll bet it's more than a little tricky.

I can agree with them being seperate things, but the problem with poopspren isn't that isn't that we lack a cognitive Ideal for poop, it's that poop doesn't stay poop long enough for an Identity to be established.
What I was trying to say (and failing) was that individual cognitive Identities are the source of "fact checking" in regards to shardic interactions, but cognitive Ideals are what shape and influence Identities. Cognitive Ideals being a set of perceptions held in common by a group of people.
Spren are a bit trickier, so I'll have to explain more what I mean when I finally get my Realmantics theory posted.

I still don't like the idea of a centralized form for cognitive ideals that you seem too be suggesting. (maybe I'm wrong.) I've always felt that it's more direct than that.
The example I used before was: a window's concept of itself comes from the window-maker. Its initial cognitive form is slightly different from even a similar window if it was made by a someone else. From then on, the window is somewhat influenced by everyone else who makes contact with it.
This would mean that every window has it's own independent cognitive identity, and the cognitive ideals of windows are only similar because people who interact with windows share perspective.
It also makes it easier for Vasher to hide himself if people don't perceive him as returned.